Tectonics of Indonesia

Seismic stratigraphy of Eocene Beriun Sands of West Bungalun, East Kalimantan, Indonesia: A contribution to the Paleogene stratigraphical knowledge of the Kutei Basin

Proceedings of the International Symposium on Sequence Stratigraphy in SE Asia, Indonesian Petroleum Association, May 1995

Seismic stratigraphy of Eocene Beriun Sands of West Bungalun, East Kalimantan, Indonesia: A contribution to the Paleogene stratigraphical knowledge of the Kutei Basin

Awang Harun Satyana*, Elan Biantoro*

* PERTAMINA, Jakarta

ABSTRACT

The Kutei Basin, East Kalimantan, is the largest and deepest Tertiary basin in Indonesia. The basin was formed in the early Tertiary and contains up to 12,000 meters of sediments in its deepest part. Basin subsidence during the early Eocene to early Oligocene resulted in the accumulation of a generally transgressive sequences of sediments throughout the Kutei Basin In the latest Oligocene, regressive deltaic sedimentation began and became the dominant depositional regime in the basin. These Neogene deltaic deposits constitute the reservoir rocks of the prolific fields in the Kutei Basin. However, hydrocarbon accumulations have never been discovered in the Paleogene sediments of the Kutei Basin, although Paleogene accumulations occur in the Tanjung Field in the adjacent Barito Basin to the south. Accordingly, the Paleogene sediments of the Kutei Basin have not been extensively studied. The Eocene Beriun sands of the West Bungalun area, Northeast Kutei Basin are the reservoir-quality rocks equivalent to the hydrocarbon-bearing Tanjung sands of the Barito Basin. Multiple vintages of seismic data (1971-1993) were used to reveal the subsurficial nature and distribution of the Beriun Formation. On seisimic data, the Beriun sands can be recognized by their distinctive amplitude and velocity characteristics, as compared to other units within the formation. Seismic stratigraphic interpretation shows that the Beriun Formation consists of at least three seismic stratigraphic sequences. Deposition of these sediments was contemporaneous with, and affected by, growth faulting, resulting in varying sedimentary thicknesses laterally. Based on this seismic sequence study, we suggest that the Beriun sediments were deposited as fan delta deposits in an extensional tectonic regime. This study supports that the Beriun sands are potential reservoir rocks in the Kutei Basin.